Techniques for bonding with substrates that have low surface energy, such as polyethylene and polypropylene, have long been studied. It has been known to be not easy to design an adhesive that shows high adhesion to these materials. A proposed technique of achieving excellent adhesion to these low surface energy substrates comprises subjecting an adherend surface to pretreatment, such as corona discharge treatment or plasma treatment, to thus increase the surface energy in advance, followed by bonding. Although these techniques are effective, expensive devices are required, as well as increased power consumption.
In contrast, products comprising olefin-based materials, such as polyethylene or polypropylene, have recently continued to increase in a variety of ways, ranging from common household appliances to those for various industrial applications. Under such circumstances, more effective adhesives that were not previously available have also recently been increasingly developed. This fact is also disclosed in Non-patent Literature (NPL) 1, on page 139 in the section entitled “2.1 State of Adhesion Techniques.” Patent Literature (PTL) 1, PTL 2, PTL 3, PTL 4, and PTL 5 disclose specific examples.